Time-controlled electrical contact mechanism.



A. L. SOHM.

TIME CONTROLLED ELECTRICAL CONTACT MECHANISM.

APPLICATION FILED NOV. 3, I913.

1,149,866. Patented Aug. 10, 1915.

UNITED STATES PATENT OFFICE.

ALFRED L. SO HM, OF CHICAGO, ILIiINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, T SOHM ELECTRIC COMPANY.

TIME-CONTROLLED ELECTRICAL CONTACT MECHANISM.

Specification of Letters Patent.

Patented Aug. 10, 1915.

Application filed November 3, 1913. Serial No. 798,819.

useful Improvements in Time- Controlled Electrical Contact Mechanism, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to electrical ClI'Cllltchanging mechanism and is concerned with a switch for use in clock systems wherein a master clock controls one or more secondary electromagnetically-operated clocks.

In systems of this kind it is usual to provide circuit-changing mechanism which is supposed to be operated periodically by the master mechanism to close the circuit at definite intervals so that the advancing mechanisms of the secondary clocks may receive their periodic-impulses, whereby a time indicating operation is secured. Great difliculty has been experienced in the art because of the unreliability of the contact mechanism wherein it was frequently experienced that on occasions either no contact would be made at all or two contact were made when but one should have been made, so that the advancing mechanisms of the secondary clocks received two impulses where they 'should have received but one and were thus thrown out of step with the master mechanism.

The difliculties outlined in the preceding paragraph are usually due to play in the time-controlled mechanisms or backlash in the gears which are employed, and it is the object of my invention to provide a structure in which such conditions have no ill effect. In other words, I provide a .structure in which play in the" operating members or backlash therein is immaterial, and I thus provide a structure in which it is impossible not to make the contact when the contact is desired and wherein it is impossi ble to make more thanone contact where but one contact should be made.

In the accompanying drawing I have illustrated a master clock and a system involving the featuresof my invention.

Figure 1 is a front elevational view of a master clock, the face beingb'rokenaway to d sclose the contact mech a more or less diagrammatic view illustrating the contact mechanism removed from the clock and installed in a circuit involving a battery and a secondary clock. and 4 are views illustrating difi'erent con ditions of the contact mechanism.

It will be seen from Fig. 1 that the contact mechanism of my invention is applied directly to the shaft of the second hand of the master clock and it will be apparent to those skilled in the art that this is a very desirable feature, since the proper makes and breaks in the circuit may be secured without the intervention of complicated gearing mechanism.

The casing of the clock is illustrated at 5, the face or dial is illustrated at 6 and the hour and minute hands are illustrated at 7 and 8 respectively.

It will be understood that the main shaft 9 is properly connected in the manner of all standard clocks with the second hand shaft 10. i

The operating member of the contact mechanism of my invention is in the form of a somewhat spiral cam 11 which is secured upon the shaft 10 and always operates therewith. This cam is preferably constructed of some hard insulating material, such as bone, and the cam periphery is fash' ioned so that a gradual rise is secured from the point a to the point I). The fall from the point I) back to the initial point a is divided into two stages separated by a step 0 upon which a contact member 12 is laid and securely fastened in place.

A collecting ring l3.is secured to the cam 11 and rotates therewith, this collecting ring being permanently electrically united with the contact member l2by means of a strip 14 The cam rotates in the direction of the arrow an.

A contact wiper 15 is mounted in a column 16 of insulating material and permanently engages-and rubs upon the rotating collector ring 13. A cam follower contact spring 17 is also mounted in the column 16 and engages the periphery of the cam, being thus subject to the gradual rise from the point a to the point b, then to the drop to the step 0, and then' the second drop back to the initial point a.

The ,eleot rical' oontact spring 17 is connected bymeans of a conductor 18 with one terminal ofrthe-winding of an electromag- Figs. 3

will merely enga e der formed b '51 net 19 of a secondary clock mechanism. I have not illustrated this secondary clock mechanism in extensive detail, but have shown merely an instance of construction. The 'electromagnet 19 is provided with an armature 20 which operates a shuttle 21 for intermittent engagement with a disk 22 mounted upon the main shaft 23 of the sec- .master mechanism is made, for instance,

once a minute, and therefore sixty impulses will be required to advance the disk 22 a complete revolution. In other words, the minute hand 24 is advanced one minute for every impulse in the electromagnetic device 19.

It will be seen that since the cam 11 is secured to the shaft of the second hand it makes exactly one complete revolution every minute, and during this minute the spring follower 17 starts from the position illustrated in Fig. 4, where it is in engagement with the initial point a. The rotation of the cam in the direction of the arrow 1' gives the follower a gradual rise until the point I) is reached, as illustrated in Fig. 3, and then the follower 17 drops suddenly down on to the contact member 12 on the step .0. The spring is held firmly down upon the contact member 12 by means of its own resiliency, and it will be clear that any backlash or loose play of the operating mechanism will result in nothing more than the rubbing of the follower upon the contactmember. It is impossible tobreak the contact by backlash, since the follower e step and will not disengage itself rom the contact member. As

a the rotation continues, however, the spring 17 drops off of the step c and down to the initialpoint a. Here, again, any backlash of the mechanism makes it impossible to make the contact again, since such backlash would merely result in jamming the follower more tightly against the second radial shoulder.

Any backlash which occurs while follower 17 is on contact member 12 has a useful purose rather than a detrimental result, since it tends to rub and clean the Conta t memthe nearly radial shoulbers at this point. It will be understood that the contact member is always in electrical engagement with the member 15 and it will be clear that whenever the follower 17 is in engagement with the member 12 the circuit through the electromagnet 19 and the battery B is closed and the single impulse desired is effected.

I claim as new .and desire to secure by Letters Patent:

1. In electrical contact mechanism, a rotatable snail cam of insulation, a spring follower contact, said cam having a gradual rise and a quick fall having a short intermediate dwell, a surface contact on said intermediate dwell for closing circuit momentarily with said spring contact and radial shoulders of insulation joining said intermediate dwell with said cam portion.

2. In electrical contact mechanism, a rotatable snail cam of insulation driven in unison with the second-hand of a clock, said cam having a long spiral portion and a short intermediate circular dwell and radial shoulders of insulation joinin said spiral portion to said circular dwel, a circular metallic contact plate on said circular dwell, and a spring follower contact making momentary contact with said plate.

3. In electrical contact mechanism, a snail cam of insulating material, said cam being driven by the second hand shaft of a master clock, said cam comprising a spiral portion anda short intermediate circular portion located between the radial ends of the spiral portion and joining the ends of the spiral portion by shoulders of insulation, a metallic surface contact plate on said circular portion, a spring follower contact making momentary connection with said metallic plate, a slip ring rotating in unison with said cam, said'ring being connected with said plate, and a spring brush in contact with said slip ring.

4. In an electrical contact mechanism, a rotating cam having a bearing surface of insulation, a spring follower contact bearing on the surface of said cam, said cam having a substantially radial shoulder of insulation, an intermediate dwell, a surface contact on said intermediate dwell, and a second substantially radial shoulder of insulation between said contact and the edge of the cam.

In witness whereof, I hereunto subscribe my name this 31st day of October, A. D.,

ALFRED L. SOHM.

Witnesses:

ALBIN C. AHLBERG,- Aucus'r H. L. ARNDT.

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